Intermittent stop mechanism for recording pencils



y 8, 1950 LA VERNE R. PHILPOTT 2,515,893

INTERMITTENT STOP MECHANISM FOR RECORDING PENCILS Filed Dec. 8, 1944 ll Sheets-Sheet l EIG. 1 I INVENTOR LA VERNE R. PHILPOTT ATTORNEY y 8, 1950 LA VERNE R. PHlLPOTT 2,515,893

INTERMITTENT STOP MECHANISM FOR RECORDING PENCILS Filed Dec. 8, 1944 ll Sheets-Sheet 2 INVENTOR LA VERNE R. PHlLPOTT ATTORN EY y 1950 LA VERNE R. PHILPOTT 2,515,893

INTERMITTENT STOP MECHANISM FOR RECORDING PENCILS' Filed Dec. 8, 1944 ll Sheets-Sheet 3 INVENTOR LA VERNE R. PHILPOTT ATTO R N EY July 18, 1950 LA VERNE R. PHlLPOTT 2,515,393

INTERMITTENT STOP MECHANISM FOR RECORDING PENCILS Filed Dec. 8, 1944 ll Sheets-Sheet 4 FIGJZ FIG.11

INVENTOR. LA VERNE R. PHILPOTT ATTORNEY y 1950 LA VERNE R. PHILPOTT 2,515,893

INTERMITTENT STOP MECHANISM FOR RECORDING PENCILS ll Sheets-Sheet 5 Filed Dec. 8, 1944 INVENTOR LA'VERNE R. PHILPOTT ATTO R N EY July 18, 1950 LA VERNE R. PHlLPOTT 2,515,893

INTERMITTENT STOP MECHANISM FOR RECORDING PENCILS Filed Dec. 8, 1944 ll Sheets-Sheet 6 INVENTOR 1 LA VERNE R. PHILPOTT ATTORNEY July 18, 1950 INTERMITTENT STOP MECHANISM FOR RECORDING PENCILS Filed Dec. 8, 1944 LA VERNE R. PHILPOTT 2,515,893

11 Sheets-Sheet 7 fi 87 FIG. 19 H ///A A) a 7 332 (4'0 @"r 422 I gxg 424 423 4'4 INVENTOR.

LA VERNE R. PHILPOTT BY FIG. ,W 5

ATTORNEY July 18, 1950 LA VERNE R. PHlLPOTT 2,515,893

INTERMITTENT STOP MECHANISM FOR RECORDING PENCILS Filed Dec. 8, 1944 ll Sheets-Sheet 8 FIG. 21

FHCNAL F- LT E R r A eiziafi fi' 525 INVENTOR LA VERNE R. PHILPOTT PI G. 24 %M/W ATTO R N EY July 18, 1950 LA VERNE R. PHILPQTT 2,515,893

INTERMITTENT STOP MECHANISM FOR RECORDING PENCILS Filed Dec. 8, 1944 l1 Sheets-Sheet 9 VOICE PICTURE PICTURE PRINTER RECEIVER CHANNEL FILTER ARMATURE l SYNCH CHANNEL FILTER 510 NAL 503 LIMITER jnCh. slgnal INVENTOR LA VERNE R. PHILPOTT BYi ATTORN EY July 18, 1950 LA VERNE R. PHILPOTT 2,515,893

INTERMITTENT STOP MECHANISM FOR RECORDING PENCILS Filed Dec. 8, 1944 ll Sheets-Sheet 10 !N\/ENTOR LA VERNE R. PHILPOTT aim/W ATTORNEY July 18, 1950 LA VERNE R. PHILPOTT 2,515,893

INTERMITTENT STOP MECHANISM FOR RECORDING PENCILS ll Sheets-Sheet 11 Filed Dec. 8, 1944 1 18.29 raox INVENTOR LA 'VERNE R. PHILPOTT ATTORNEY Patented July 18, 1950 INTERMITTENT STOP MECHANISM FOR RECORDING PENCILS La Verne B. Philpott, Washington, D. C., assignor, by mesne assignments, to Pierce Company,

Providence, R. 1.

Application December 8, 1944, Serial N 0. 567,236

1 My present invention relates to a'facsimile receiver and more particularly to a facsimile receiver adapted to receive and reproduce transmitted images on ordinary unprepared paper.

More specifically, my invention relates to a facsimile receiver which will use as the scanning element a vibrating pencil member arranged and operated to make marks varying in shading in accordance with the shading or density of the elemental areas of the transmitted image.

Various methods have been used for recording facsimiles at a receiver. These methods have included recording elements which consisted of a variable, intensity light beam cooperating with photo-sensitive paper; a stylus member cooperating with specially prepared thermally sensitive or electro-sensitive paper; printing units which included a pen for depositing ink in dots or lines varying in spacing or thickness in accordance with variations in the elemental areas of the transmitted image; and printing elements using bars or other vibrating members which press a marking member or marking element, such as carbon paper, against a recording sheet, spacing the marks thus produced in accordance with variations in the transmitted image.

Substantial variations in shading have been obtainable with photo recorders and even with the electro-sensitive or thermo-sensitive papers which utilize a stylus. The substantial difiiculty that occurs, however, with photo recorders is that the photo-sensitive sheet must be handled under light-proof conditions and must be developed after the recording operation. These conditions are not compatible with high speed facsimile transmission or with simple continuous facsimile transmission; the photo-sensitive recorder, by reason of the many operations that must be per formed with respect thereto, is not adapted for operation or use by any but highly trained technicians. Its commercial use is, therefore, limited to those instances only where such highly trained technicians are constantly available.

In the case of electro-sensitive or thermosensitive recording on prepared paper, continuous facsimile recording without undue handling and without any great skill on the part of the operator is possible. However, the recording sheet which is used must be specially prepared and treated, and many of the characteristics of this recording sheet are marginal.

Thus, in recording sheets for the stylus type of recording where a conductive black base paper is used having a White metallic coating which is discolored by the passage of electric current,

3 Claims. (Cl. 346139) minute variations in the density of the coating will cause corresponding variations in the recorded picture and even slight and unforeseeable defects in the evenness of the coating will tend to mar the picture. Since'such coatings are usually very thin, and since the sheet in use is taken from a roll passed through various feed rolls and other elements and is subject to a great deal ing wider or narrower lines, printing wider or" narrower bars or spacing dots widely or closely to produce a species of half -tones.

A principal object of the invention is the provision of a scanning member for a facsimile recorder which will utilize an ordinary unprepared recording sheet and which will nevertheless produce marks varying in shade in accordance with the variations in shading of the elemental areas of the transmitted image. These marks .will not simply be a series of blacks spaced by wider or narrower unmarked areas but will be substantially continuous marks varying from a very light grey to black.

Another object of my invention is the provision of a facsimile recorder utilizing a pencil member as the recording element, the said pencil member being so operative and arranged that it will produce marks of varying shades on the recording sheet of the recorder.

Another object of my invention is the provision of improved facsimile apparatus by means of which helical scanning can be accomplished with respect to a continuous recording sheet.

Previously, helical scanning was obtained by winding a recording sheet about a drum and causing the drum to rotate while the stylus or other recording element moved longitudinally of the drum. In another type of helical scanning, the stylus or other recording member rotated helically around the drum. In either of these types of recorders, helical scanning of a continuous sheet was impossible. In the so-called lawn mower type of recording, the recording element has a helical wire on a rotating drum, but the sheet moves longitudinally with respect to the drum, is

These minor defects, however, are

not wound around the drum, and the recording operation is not a helical one; the helical wire is simply used in cooperation with a straight bar on the other side of the sheet to produce a series of transverse lines on the moving sheet.

True helical scanning, where the stylus or drum rotated to define a continuous helical line on the sheet, has heretofore been impossible with continuous sheet recording,

My present invention, by feeding the recording sheet around the inside of the drum and causing the marking member to rotate continuously within the drum, makes continuous sheet recording in connection with continuous helical scanning possible.

The foregoing, and many other objects of my invention, will become apparent in the following description and drawings in which:

Figure 1 is a top plan View, partially broken away, showing schematically the drive elements of my novel facsimile recorder.

Figure 2 is a fragmentary view in perspective of. the means for driving the record marking member of my novel facsimile recorder.

Figure 3 is a perspective view of one of the plates 52 of Figure 2 showing the relationship of the parts thereof.

Figure 4 is a top view of the carriage member 5| of Figure 2 showing the relationship of the various supporting plates of the said carriage member.

3 Figure 5 is a back view of the carriage member shown in Figure 2 showin the relationship between this carriage member and the means for rotating the marking member.

Figure 6 is a cross sectional view through the carriage member of Figures 2 and 5 showing all of the marking elements and the operation thereof.

Figure '7 is an expanded view of a portion of Figure 6 showing the pencil holding and adjust ing means.

Figure 8 is a View in perspective of the pencil stop member of Figure 6.

Figure 9 is a view in perspective of the cross plate supporting member of Figures 4 and6.

Figure 10 isv a View in perspective of the, cam shown in Figure 6.

Figures 11 and 12 are enlarged, fragmentary schematic views showing the relationship between the marking pencil and, the recording paper.

Figure 13 is a view of the outer surface 0fv the gear 30' of Figures 1 and 2 showing the elements mounted, thereon.

Figure 14 is a View of the face of gear 26l of Figure 1 showing the spiral groove therein which cooperates with the element 3 [2 of Figure 13, and the. bushin 280 which carries the gear 36 of Figure 13.

Figure 15 is an expanded view of the clutch 263 of Figure 1.

Figure 16 is a schematic view of the clutch of Figure 15.

Figure 17 is a schematic view illustrating an additional modification of the clutch member to be used in connection with portions of the clutch of Figures 15 and 16.

Figures 18 is a view in perspective of the element 3 of Figure 13.

Figure 19 is a longitudinal section through my novel facsimile recorder showing the means for feeding and securing the paper in the recording drum. For purposes of clarity, the elements 4% within the recording drum shown in Figure 6 have been omitted from this figure.

Figure 20 is a top view of my novel facsimile recorder.

Figure 21 is an expanded view of the drum and paper clamping elements of Figures 19and 20 showing the relationship therebetween.

Figure 22 is a view in perspective of the clamp operating element 392 of Figure 19.

Figure 23 is a view in perspective of the manual operating handle 402 for the clamp elements of Figures 19 and 21.

Figure 24 is a schematic view demonstrating the operation of the clutch 5M of Figure 1.

Figure 25 is a schematic view showing support elements for achieving appropriate synchronism between the recorder and the received impulses.

Figure 26 is a diagram showin the relationship between the synchronizing signal and the elements of the recorder.

Figure 27 is a longitudinal section through my novel facsimile recorder showing the relationship of the various elements and. showing a slightly modified paper feed.

Figure 28 is a side view of my novel recorder showing the paper feed of Figure 27 and a slightly modified means for. taking up the recorded picture.

Figure 29 is a top View of the device of Figure 28.

Referring now to Figure 1, which shows a schematic lay-out of my facsimile apparatus, the motor Hl drives the shaft H, which through the clutch [2 drives shaft [5. Shaft i5 drives the principal. driving gear 16. Other elements (hereinafter described) necessary for operating the receiver mechanism are also driven from shaft 15 the shaft 26 so that rotation of gear 25 results in corresponding rotation of gear 25'.

Similarly, the main drive gear 3i] is duplicated by the opposite main drive gear 36' also rotatably mounted around the normally stationary shaft 3!. Gears 30' and 30 are integrated for simultaneous rotation by the threaded shaft 32 and the slotted shaft 33. Threaded shaft 32 is rotatably. mounted in the. bearings 34, 3 3 in the opposite gears30 and3i1 andthus may readily rotate with respect to the gears 30 and 30' on which it is mounted.

The shaft 32v carries a small gear 35 keyed thereto. The small gear 35 meshes with the gear 36 of equal diameter keyed to the bushing 280 of gear 26!. Gear 26! rotates at adifferent speed than gears 30 and 35 (as hereinafter described) so that the rotation of gear 36. is at adifferent speed than the planetary movement of gear 35. Thus, as. the large gearsiifl and 30' are rotated by the gearsv 2.5. and 25. around the stationary shaft 31, the threaded shaft 32, which rotatesv 5. manner hereinafter pointed out. Ordinarily, the slotted shaft 33 does not rotate in its bearings 38 in the large gears 33 and 30. It is rotatably mounted, however, so that it may be angularly moved for the recorder resetting purposes hereinafter described.

The normally stationary shaft 3| is provided with a helical thread 42 along substantially its entire length between the gears 30 and 30', in order to rotate the recorder pencil carriage in the manner hereinafter described.

Other elements of the device shown in connection with Figure 1 will be more readily explained in connection with subsequent figures. In Figure 1 (however) I have omitted the pencil carriage and mount in order that the drive mechanism itself may more readily be seen, and I have compressed the structure laterally for clarity.

In Figure 2, I have shown in a schematic perspective view the mounting of the pencil carriage and mount on the shafts 32 and 33. The gear 30, shown in Figure 2, is duplicated on its opposite side by the gear 38 (not shown in Figure 2). The threaded shaft 32 is carried between the opposite gears 33 and 33 as already described in Figure 1. Similarly, the slotted shaft 33 with the groove or slot 4|! is carried between the opposite gears 3|! and 30, and the shaft 3! having the helical thread 42 extends between these opposite gears.

All of the elements can now in Figure 2 be seen more readily in their relation to the hollow recording drum 53 and the recording pencil carriage 5| (the hollow recording drum 53 is also indicated in Figure 1, but the recording pencil carriage is not shown in Figure 1). It is understood, however, that the recording pencil carriage is always mounted on the device. In Figure 2, the elements carried by the recording pencil carriage are not shown in order that the manner in which the recording pencil carriage is carried by the shafts may more readily be understood.

The recording pencil carriage comprises a pair of opposite parallel plates 52, 52 between which is carried the pencil motor plate 53. The pencil motor plate 53 is provided with an appropriately recessed race-way 54 for ball bearings, hereinafter more specifically described in connection with the specific description of the operation of the recording pencil.

Each of the plates 52, 52 has the form shown in Figure 3. The opening 50 through which the shaft 33 passes is provided with an insulated bushing 6| so that there will be no electrically conductive relation between the shaft 33 and the plate 52 for purposes. hereinafter described.

The opening 53 at substantially the center of each of the plates is provided to permit the shaft 3| with its helical thread 42 to pass through the plates and through the carriage 5|.

Each of the openings 64, in each of the plates 62 is threaded, as at 55 (Figure 3), in order that the plates 52 may be in threaded engagement with the threaded shaft 32 (Figure 2). Thus, the carriage 5|, as will be seen from a comparison of Figures 2 and 3, is slidable along the shafts 3! and 33 but is in threaded engagement with the shaft 32.

The carriage 5! is held rigid with respect to the gears 30 and 3|.! so that it will not rotate with respect thereto by reason of the fact that shafts 32 and 33, which are secured to the said gears, pass through opposite sides of the carriage. Consequently, as the gears 3|! and 30 rotate, the carriage 5| will rotate. But, since the threaded shaft 32 rotates on its own axis, owing to the en- 6. gagement of its gear 35 with gear 36, the threaded shaft 32 will cause the carriage 5| to move longitudinally from one side of the apparatus (adjacent gear 33') to the other side of the apparatus (adjacent gear 30). This will result in appropriate scanning operation with respect to the hollow drum 5D.

The scanning pencil has been indicated schematically in dotted lines at 10 of Figure 2, and the scanning drum 5D has also been indicated schematically in phantom in Figure 2. It will thus be seen that as the carriage 5| is rotated and moved longitudinally by the revolution of the gears 33, 33' and simultaneous revolution of the shaft 32, a helical scanning line will be traced on the interior of the hollow drum 53 or on any paper sheet extended over the interior of the said hollow drum 50.

In Figure l, I have shown a top plan View of the pencil carriage 5| showing the organization and relationship of the side plates 52, 52 with the front pencil motor carrying plate 53 and its ball bearing race-way 54, and with the apparatus supporting platform T3 hereinafter more specifically described.

Before going, however, to the specific description of the pencil motor plate, it should be pointed out that the pencil motor comprises essentially a carriage carried in the race-way 54 of the pen-. cil motor carrying plate 53, this carriage being so arranged that it will be rotated with respect to the plate 53 as the carriage 5| moves longitudinally along the shafts 32, 3| and 33. This operation is more clearly seen in the back View of Figure 5 from which all parts contained by the carriage 5| behind the pencil motor itself have been removed in order that the operation may be more fully understood.

The pencil motor 15 is essentially a rotatable disc which rotates in the race-way 54 of the pencil motor carrying plate 53. The pencil motor disc 15 has a pluralit of pins extending there-- from and so arranged that they engage the helical thread 42 of the shaft 3|. As the carriage 5| moves longitudinally with respect to shafts 3|, 32 and 33, the engagement of the pins of the pencil motor disc 15 with the stationary helical thread 42 causes the pencil motor disc 15 to rotate. The rotation of the pencil motor disc 15 thus depends on the longitudinal movement of the carriage 5| which is obtained in the manner previously pointed out with respect to Figure 2. The rotation of the pencil motor disc 15 continuously sharpens the point of the pencil as hereinafter pointed out.

In Figure 6, I have shown a cross-sectional view through the carriage 5| showing the arrangement of the various parts and the mounting of the pencil within the carriage 5|. The hollow drum 50 is indicated in phantom.

The carriage 5|, as above pointed out, comprises the opposite parallel plates 52 having the opening 60 for the slotted shaft 33, the opening 63 for shaft 3| having the helical thread 42 and the threaded opening 64 for the threaded shaft 32.

A cross plate or platform 13 (also Figs. 4 and 9) is supported between the plates 52 in any suitable manner as by welding or riveting, as indicated at 80, of Figure 3. Similarly, the front pencil motor-carrying plate 53 is secured in position between the plates 52, 52 in any suitable manner as by welded or riveting as indicated at 8|, 8| of Figure 3. The principal supporting disc 15 of the pencil motor is rotatably '2 supported in the race-way 54 of the pencil motorcarrying. plate 53. Friction may be reduced in any suitable manner as, for instance, by the use of the ball bearings 84.

The main pencil motor disc carries a substantially. circular housing 85 having. a cylindrical wall 86 and a preferably integral conical: wall 81. connected thereto, the said conical wall 81 terminating at its apex in a slightly flattened section- 88 having an opening 89 through which the pencil 'Iltmay project.

The pencil Ill is held in a clamping arrangement comprising a lead vise 99, which (see Fig.- ure 7 as well as Figure 6) is essentially a tubul'ar member adapted to contain the length of pencil ID.

The front end of the tubular member 99 is slotted, as at 9|, at various spaced points around its periphery so that this end may be compressed slightly to grasp the pencil ill. The forward end of the tubular member 96 is provided with an annular ledge 920, normal to the aXis of the tubular member 90 against which one end of the compression spring 92 bears. of the compression spring 92 bears against the nut 93 of the armature 95.

The armature 95 has a central substantially tubular section 96 having a hollow opening 91 therein terminating in a conical end 98' with an opening 99 at the apex of the cone.

The ledge 92a of the tubular member 90 is formed by a conical annular projection I09 around'the end of the tube 99. The base of the opening 9i opposite the conical end 99 is closed by the nut 93. The spring pressure generated by the compression of the spring 92 between nut 93 and the annular ledge 92a drives the left-hand end of the tube 90 so that the conical end I99 thereof is compressed by the conical interior 98 of the opening 9'! of the armature. consequent-- ly, the pencil l0 which projects through the lefthand end of the tube 99 through the opening. 99: in the armature and the opening 89 of the housing is clamped into appropriate engagement by reason of the fact that the spring drives the clamping members i139 tightly against the inxterior of the cone 98 and thus. tightly into enthe exploded view of Figure 7, is a substantially cylindrical member having the cylindrical wall- I IILand the conical wall III, having the Open.- ing 99 at its apex.

The armature 95 is supported in the outer bearing race I carried by the motor disc: 15. Balls I 2I mounted between the armature tube 96 and the outer bearing race I29; provide for relatively frictionless longitudinal motion of the armature but prevent an rotational motion-of the armature with respect to the disc l5; thatiis, the balls IZI are arranged longitudinally in appropriate longitudinal race-ways. soas to-permit free longitudinal motion but no rotation.

The annular wall 86 of the motor housing is provided with an annular insulatingv ring l-39 around. which is mounted the annular conductive slip ring I3I.

A brush assembly I is mounted; in any suitabl manner as, for instance by the screw I36,

The opposite end 7 8, at one end. of the pencil; motor carrying. plate 53. The brush assembly I35 comprises. aninsulated bushing I31, supported by the bracket- I 9 9, in whiclris mounted the brush l39 urgedinto conductive relation with the conductive slip ring I3I by the compression spring I 32.

An appropriate electrical connection is made in any suitable manner between the shaft 33,- which isof conductive material, and the brush I39. Shaft 33 may readily be used for this purpose since it is ordinarily not a rotatable shaft, and, When it does rotate, it rotates through only a relatively small angle and then returns to its. original position. In order to permit this type of connection to be" made, the opening 60( Figures 3' and 6) in each of the plates 52 of the carriage BI is provided with the insulating bush.- ing 6|. Current thus flows from the conductive shaft 33 through an appropriate electrical con-- nection to the brush I 39 to the slip ring I3I; from the slip ring I3I it flows through the conductor I 49 to the conductive rivet Mi. Rivet MI is insulated from the pencil motor housing by the insulating bushing M2. From. the portion of the rivet I l! on the interior of the housing 8i, current flows through the conductor. I44 to the coil I45 of the armature 95. Current then flows from the opposite terminal of the coil M5 through the conductor Me to the rivet.

I 41 to ground.

Accordingly, received picture signals will be impressed on the armature coil I45 and thus cause the armature 95, which carries the coil I45, to vibrate in accordance with the intensity of the picture signals with respect to the permanent:

magnet I59.

Small spring i5iia may be provided between the motor pencil plate 53 and the nut I5I to counterbalance the very slight weight of the pencil assembly at the bottom of its stroke when the ap-' paratus operates in a horizontal position. I have found that best results may be obtained when the. axis of the recording drum is vertical, thereby obviating the unbalancing effect of gravity.

In Figure 6, the pencil is shown just prior to the commencement of a scanning operation with the pencil retracted and held. in place by the stop I69. The stop member i6!) is also shown in Figure 8, where it is seen that it is a portion orv a lever operated by the resetting shaft- 33.. The stop member I99 is provided with a pair of arms. Iii-I I'EI which pass on opposite sides of the pencil motor housing 8'? and which connect with apair. of arms I62, I62, each extendingon the outside surface of the carriage plates 52.

The'openings- I63, H63 in the arms I62 (Figure 8 a-rerotatably supported on the pins I94, I64 (Figures 2 and 3) on the outside surfaces of the carriage plates 52v so that the stop member I69- and its associated supporting arms IGI and I62 are rotatable about the pivot pins I64. The connecting rod I55 between the free ends of the arms I62 passes through the arcuate openings I61: (Figures 2 and 3) in the opposite carriage plates 52.

It will be obvious that pushing downthe rod I will rotate the arms I69, I92 so that the op'-- posite ends carrying the stop member IE9 will move up.

An appropriate coil spring around the pivot pin I64 shown in Figure 3 and bearing upwardly on arms I62--I6I which carry stop member I60, will bias the stop I50 upwardly to a point where it will block the pencil, as shown in Figure 6,

and thus prevent the pencil from emerging from the opening 89 in the pencil motor housing.

A cam H is provided between the carriage plates 52 and is supported by the slotted shaft 33. This cam is provided with an inwardly extending tongue III which engages the slot 40 in the slotted shaft 33 so that the cam I'II! will be rotated by the shaft 33 when the shaft 33 rotates. On completion of the scanning of the picture, the shaft 33 will be rotated in a counterclockwise direction (with respect to Figure 6), thus rotating the cam I10 in a counterclockwise direction.

The cam I10 is provided with an extension or ledge I12 which supports the cross rod I55 of the stop member I60. Rotating the cam I'I0 counterclockwise will result in counterclockwise movement of the cam extension In and. will permit the cross rod I65 to move downward toward the right in the arcuate opening I61. This will permit the stop member I60 to move upwardly in front of the opening 89.

Rotation of the cam I10 simultaneously results in rotation of the ledge I15 thereof. Ledge I15 engages the nut I5I on the end of the tube 90 to pull the tube toward the right slightly and thus release the pressure of the conical members I00 on the pencil I0. This also, of course, withdraws the pencil slightly into the opening 89 so that the stop member I80 may move freely across the opening. The pencil now is retracted from the paper lining the interior of the drum 50.

At the same time, and in order to permit the operations above set forth, the extension I'I8 on the cam H9 is raised by counterclockwise rotation of the cam thus lifting the clamping member I89. The clamping member I80 is rotatably supported on the pivot I8! journalled in lugs I82 on the cross shelf I3. It is biased downwardly into clamping engagement by the compression spring I83, the lower end of which bears against the loose washer I84 on the upper surface of the clamping member I80 and the upper end of which spring bears against the stationary washer i 85 held by the bolt I86.

Bolt I88 passes through an opening of substantially larger diameter I91 in the clamping member I89 and is supported in the cross plate 13. Accordingly, the compression spring I83 biases the clamping member I80 in a counterclockwise direction and downwardly with respect to the cross shelf or cross piece I3.

The lower end of the clamping member I88 is provided with a clamping portion I90 passing through an opening I9I in the cross shelf and en gaging a rod I92 supported in a tubular opening I93 in the cross shelf. The construction of the cross shelf I3 and of the cooperating elements above described is shown in Figure 9.

The tubular opening I93 in the base of the cross shelf I3 is aligned with the tube 90 so that the rod I92 may project from the tubular opening I93 into the tube 90. The lower surface of the tubular opening I93 is slotted at 200 (see Figures 6 and 9) so that the end I of the lever 202 may enter into the tubular opening I 98 to push the rod I92 to the left.

In ordinary operation, with the cam H0 rotated about clockwise from the position shown in Figure 6, the cross rod I 65 is at the upper end of slot I81 and the stop I60 is below the opening 89. The ledge I'I5 of cam I'I0 does not engage the nut I5I. Accordingly, the compression spring 92 ensures that the conical members I00 will clamp the pencil I0 tightly and the pencil is free to move up to the paper lining the interior of the drum 50. The pencil is prevented from moving back by reason of the fact that the clamping portion I90 of the clamp I is held down against the rod I92 by the spring I83, and rod I92 bears against the end of pencil I0.

When the elements are positioned, as shown in Figure 6, the ledge I'I8 engaging the hook 2I0 of clamp I80 raises the clamping portion I90 out of engagement with the rod I92. Pressure of the end 20I of lever 202 on the end of rod I92 will now push the rod I92 to the left and consequently push the pencil I0 to the left until it engages the stop I80.

Rotation of the slotted shaft 33 in a clockwise direction will now permit the spring I83 to press the clamping portion I90 of the clamp I80 on the rod I92; and simultaneously the nut I5I will be released by the ledge I? 5 of the cam to permit the compression spring 92 to tighten the clamping head I00 on the pencil. At the same time, the rod I85 of the stop I60 will be raised, pushing the stop I down away from the opening 89 so that the pencil I0 may emerge through the opening 89.

The portions of the cam I10 may more readily be seen in the perspective view of Figure 10.

The lever 202 is mounted for movement toward the left by means of the arm 203 to which it is pivotally connected at 2H and which is rotatably mounted at 204 in an appropriate bearing 205 on the interior of plate 52 (see Figures 3, 6 and '7). The pivotal end 204 of the arm 203 is a shaft carried between the opposite bearings 205 in the opposite plates 52.

A coil spring 2), indicated in Figure 7, imparts a counterclockwise bias to the arm 203.

Each of the opposite arms 203 is pivotally connected at ZI I, 2 to the bifurcated support 2I2 for thearm 202, the said bifurcated support comprising the connected arms 2I3, 2I3. The free end of each of the arms 2I3 is provided with a pin 2I4 which engages in the slot 2I5 of the side plate 52.

When clamping pressure is removed from the rod I92 by raising the clamp I80, then the coil spring around the shaft 204 tends to rotate the arm 203 in a counterclockwise direction. This will pull the arm 202 and arm 2I3. toward the left with the end 20I of the arm 202 pushing the rod I92 toward the left to push the pencil 10 toward the left.

In order to compensate for the fact that the end 20I of arm 202 must move linearly, the center of rotation 2I4 of the arm 202-2I3 is permitted to move downwardly in the slot 2 I5. Accordingly, the rectilinear mechanism comprising the arm 202-2I3 and the arm 203 is constantly biased to move the pencil I0 toward the left. This bias is overcome by the clamp I80 while the device is in operation, but when the clamp I80 is raised and the pencil tube 90 is retracted to loosen the clamping end I00, the rectilinear mechanism terminating in the element 20I is free to move the rod I92 and the pencil '70 up to the stop I80. Thereafter, when the clamp I80 is reengaged and the stop I60 is removed, the spring 92 re-sets the clamping end I00 to hold the pencil rigidly with respect to the armature 9-5 and to cause the pencil III to protrude slightly from the opening 89.

The vibration of the armature 95 will now result in variations of the density of the marking of the pencil on the papers which lines the interiorof the drum 5! Operation of the device as thus far described is as follows: When the motor I drives the gear 16 to rotate the gears 25 and 25' and thus to result in rotation of the large gears 3% and 30, these gears will rotate the shafts 40 and 32 in a planetary manner around the stationary shaft 3|. Accordingly, the entire carriage 5| comprising the carriage plates 52, the motor pencil supporting plate '53 and the shelf 13 will rotate in the same way as do the gears 30 and 30'.'

' At the same time, the threaded shaft 32 will rotate by reason of the engagement of its gear 35 with the gear 36 on bushing 26!]. Rotation of shaft 32 causes the carriage 51 to move longitudinally.

' jVibrations of the armature in accordance with picture signals that are received and impressed on the coil 145 will cause the pencil to vibrate to vary the density of the markings made by the pencil on the paper which lines the interior of the drum 50.

The drum 5!) is, of course, stationary at all times. Accordingly, as the entire carriage rotates inside the drum and simultaneously moves longitudinally with respect to'the drum, the pencil will trace a helical line around the paper on the interior ofcthe drum '50.

The pitch of the helical trace will be determined by the pitch of the thread of the threaded shaft '32 and the relative speed of rotation about its own axis of the shaft 32 with respect 'to the speedof rotation of the entire carriage.

On completion of the scanning operation, that is, on completion of the movement of the carriage-5| from one side to the other of the drum, the shaft' 33, as hereinafter described will be rotated counterclockwise about 30 (with respect to Figure 6) to retract the pencil and loosen the clamp thereon and bring the stop I60 up in front of the pencil. The lever end '20-! will automatically re-set the pencil, and the rotation of the slotted shaft 33 back to'its original position will re-set the clamp for the pencil and remove the stop I60 to prepare the pencil Ill-for another scanning operation for another picture.

While scanning is proceeding, the pencil and, in fact, the entire mount for the pencil is rotated (in order'to maintain a sharp point on the pencil) by means of the pins '11 extending from the main plate of the pencil mount and in engagement with the helical threads 42 on the stationary shaft 3 I.

Thus far, the description has embraced the operation of the carriage to trace the helical scanning line from one end of the interior of the drum to the other, the rotation of the pencil mount to maintain a sharp point on the pencil while scanning is proceeding, and the re-setting of the pencil to appropriate pressure position (to compensate for any wear thereon) at the end of the'scanning of a picture frame.

Mydevice includes, in addition, specific novel means for automatically returning the carriage to the original scanning position; novel means for feeding the paper into and out of the interior .of the drum; novel means for cutting the paper at the end of each picture frame; and novel means for maintaining synchronism.

The principle of operation of this system is that a mark made by a pencil on apiece of paper depends upon the applied pressure and fOl OWS the empirical formula,

12 FORCE=KE where n is the shade coefficient, E is the natural logarithm base, and I; is a constant.

In Figures 11 and 12, I have shown the optimum arrangement of the pencil where the pencil is so arranged that its point which is sharpened to an angle of l i6 is inclined 17 from the normal. The point of 146 is maintained by constant rotation of the pencil about its own axis, that is, the pencil tube 99 and the pencil .are at the exact center of rotation of the pins 11. The angle of 17 between the axis of the pencil and a line normal to the paper is necessary to prevent side force on the point. The exact .angle depends on paper friction on the pencil and is independent of the marking force.

The armature 95 is soarranged that it tends to advance outwardly slightly from the magnet 150, thus bringing the pencil end into contact with the paper 250 (Figures 11 and 12). As the lead wears slightly, the armature advancesthe' pencil out accordingly to maintain slight contact with the paper. The vibration of the armature toward the paper, however, by reason of variations in energization of the armature coil M5, results in the marking.

The armature is so arranged that it may corn pensate for approximately in wear in the lead, that is, even though the lead is worn down from its condition at the startof a picture, vibration of the armature will nevertheless produce variations in shading from black to. white on the paper 258. I have found, however, by experiment, that a little more than lead is used in sending 40 square inches of solid black print. In general, less than will be used on a single picture frame. 'Thus, it is unnecessary to correct for point wear, except between frames. This is done during the'rewind process, at which time the pencil tube Si! is retracted with the pencil, the clamp Hill is released and the stop IEO moves up in front of the pencil.

The operation of the rectilinear mechanism 2il3-202 previously described resets the pencil; and on completion of the rewind operation, the pencil is clamped once more in its original position and the stop m0 is removed. It will be noted that the clamp I8!) which holds the pencil in its original position is not directly connected to the pencil but rather presses down on the rod I92 which bearsagainst the rear end of the pencil H3. Thus, the rod 192 pushes the pencil 10 up against the stop I611. The re-setting clamp 1B0 clamps the rod NZ to prevent the pencil from moving back. The pencil 16 is itself clamped into the armature by the clamping elements 100. Removal of the stop 450 now permits the armature to move the pencil out slightly and thus to move it away slightly from the left hand end of rod I92 (Figure 2). The pencil It is now entirely under the control of the armature 95 alone and is brought up very lightly into engagement with the paper 255 in preparation for recording in response to energization of coil M5.

The apparatus provided for rewinding and resetting the mechanism is shown in Figures 1, 13, li and 15.

The gear 35 is fastened to a bushing 26% which is integral with the gear 26! (Figures 1 and 14). Gear 251 meshes with gear 262 carried on the shaft 25 and which is driven through the clutch mechanism 263 shown in Figures 15 and 16. When the clutch is closed, gears 25 and 262 are driven together.

The gear ratios are so arranged that gear 261 13 is'then driven at /1oth the speed of gears 30, 39'. In other words, when operated, the gear 26! is driven 10% faster than the gears 30, 39 which rotate the carriage i.

Gears 35 and 36 are the same size so that shaft 32 is rotated once in its bearings as it revolves ten times about the shaft 3| which always remains stationary.

'Since the threads on shaft 32 are 1i) per inch,

the gears 39 will rotate one hundred times while the pencil marking device advances one inch. When the frame is printed, or at the discretion of the transmitter operator, a contact is closed to disengage the clutch 263 between gears 25 and 252, and simultaneously a brake is applied to stop the gear 262. Thus, with the gear 2E2 stopped, gears 261 and 36 must also stop. Gear 35 will therefore roll around the gear 36 rotat ing at high speed in the opposite direction and bringing the printer motor assembly back to its initial position. When this point is reached, the clutch 263 is operated to release the brake from gear 252. Gear 282 is now free to rotate but is not driven.

Since the gear 262 is free, it will permit the gear 26! to rotate. Gear 26! is now rotated because the gear 36 carried thereby is in engagement with the gear 35 of the threaded shaft 32; since the gears 36 and 262 are free to rotate together in a system which is not connected to other elements, the engagement of gear 35 of threaded shaft 32 with gear 35 will cause gear 36 to rotate simultaneously with the gear 39, thus rotating gears 26! and 262. Accordingly,

the marking device will idle until the starting signal is received.

When the starting signal is received, gears 25' and 262 are integrated by the clutch 263. so that they are driven together. The gear 262 will new drive gear 231, and hence the gear 35, at the relative speed previously noted, that is, the gear 3i: will be driven at /1oth the speed of gear 35 resulting in one hundred rotations of the carriage for each linear inch of movement thereof and thus spacing adjacent scanning lines by 100th of an inch.

In Figures 15, 16 and 17, I have shown the elements of the clutch 223. The shaft 22 a threaded end 219 which extends through a counterbored stud 2 on the gear 262 and is cap tured by the nut 2'53 held against the right end of the stud 21!. The gear 262 is appropriately positioned by the compression spring 215 between the interior surface 215 thereof and the interior surface of the nut 213. A thrust bearing 216d between the nut 2'53 and the spring 2'15 permits the gear 262 to rotate freely.

The gear 25' is provided with a clutch face 220 which passes through the center of the thrust bearing 28| to engage the clutch face 282 of the gear 262. The thrust bearing 28! ensures a substantially frictionless condition between the clutch shifting disc 292 and gear 262 when no drive is desired. Ordinarily. the spring 215 drives the clutch faces 289 and 282 together.

I When the coil of magnet 299 (Figure 16) is en ergized, it attracts the armature 29| The arma- .ture engages the clutch shifting disc 292 and moves the same toward the right with respect to Figures 15 and 16. Movement of the clutch shifting disc 292 to the right pushes the thrust hearing 28! and the gear 262 slightly to the right. 'This disengages the gear 262 from driving engagement with the gear 25'.

Further energization of magnet 290 will attract the armature an additional step toward the right and push the gear 262 up against the brake disc 295 and push this disc against the bearing 296. This will stop the gear 262.

Partial deenergization of coil 299 will permit the spring 2'55 to push the gear 262 away from the brake disc 295 to permit the gear to rotate freely.

Full deenergization of the magnet coil 29!] will permit the clutch faces 28D and 282 to re-engage once more so that gear 262 will rotate with gear 25.

In Figure 17, I have shown a slightly modified construction where, in addition to the magnet 29!! and armature 29l and other elements shown in Figures 15 and 16, a further braking mechanism is provided instead of a brake disc 295. In this case, a separate magnet coil 300 is provided to attract the armatures 31, 311i to engage the stud 211 of the gear 262.

Where the device of Figure 17 is used, the coil of magnet 296 of Figure 16 is energized to disengage gears 25' and 262, and then the coil of magnet 393 is energized to brake the gear 262. This is somewhat better than the possibly marginal operation where a single coil on a single magnet 299 of Figure 16 is used and is energized partially to disengage the gears and further energized to brake one of the gears. The preferred form is the combination of the clutch disengaging mechanism of Figure 16 as applied to Figure 15 and the braking mechanism of Figure 1'7 as applied to the stud 2' of the gear 262 of Figure 15.

Gear 26| is provided with a spiral groove 31!! (see especially Figure 14). This groove is engaged by the crank arm 31! (Figures 13 and 18) which is keyed to the slotted shaft 33.

Crank arm 3 is provided with a transverse pin 3| 2 which engages in the groove am. The crank arm 3! I is spring loaded by means of tension spring 3|3 to an intermediate position, the said tension spring 3l3 engaging the pin 3i2 of the crank arm at one end and, at the other end, engaging the pin 31 on the gear 30'.

The spiral groove 3 I 0 of the gear 26l comprises an outer circular groove 32!), an inner concentric circular groove 32! and a spiral connecting groove 322 curving centripetally in a clockwise direction from the outer circular groove 32!! to the inner circular groove 32l and forming a connecting passage therebetween.

Any movement of the crank arm 3 will be translated into angular movement of the slotted shaft 49 and will accordingly be translated into rotation of the cam I79 of Figure 6 for pencil ad justment purposes, as described previously in connection with Figure 6.

During the printing cycle, the pin 3E2 of the crank 318 is driven toward the center of the gear 261 until the pin 3l2 rides in the circular groove 32l of the gear 26!. Accordingly, during the printing operation, the'gear 26! rotates in the direction shown by the arrow 325 in Figure 14.

At the conclusion of a printing operation and on actuation of the clutch elements 263, as previously described in Figures 15, 16 and 17, the relative motion of gears 30 and 261 is reversed Consequently, the direction of rotation of gear 215i with respect to gear 30' is in the direction shown by the arrow 326 of Figure 14. The pin 3l2 of crank arm 3H will now, on this relatively reverse motion, ride out of the circular groove 32l into the spiral groove 322 and out into the outer circular groove 329. This will result in a rotation of the crank arm 3H through an angle 15 of about 30 and in a correspondingrotation of the slotted shaft all and, therefore, ina corresponding operation of the cam I19 forthe pencil re-setting operation.

The intermediate spring loading of the crank arm3l I by the tension spring 3 l 3 will ensure that the pin 312 of crank arm 3!! bears against the inner surface of groove 329 and against the outer surface of groove 32! so that on rotation of the gear 2 6! with'respect to the pin 312 in an appropriate direction, the pin 312 will enter into the spiral 322.

In Figures 19 and 20, I have shown in somewhat schematic "cross-sectional view the paper feed for the recording apparatus of Figures 1 and 6. The paper 259 is drawn from a-suitable supply roll by the driven feed roll 359. Suitable pressure for drawing and feeding the paper is provided by the spring loaded pressure roll 35!. Pressure roll 35! is mounted on bracket 352 pivotally mounted at 1353 and having the handle 353, by means of which the bracket 352 may be rotated about pivot 353 to remove the roll 35! from engagement with roll 356.

Preferably, bracket 352 isspring loaded by an over-center spring, so that in the position shown in Figure 19, the roll 35! is brought to bear against the roll 359; while, when the bracket is rotated90 counterclockwise by handle 354, it will remain in that position until snapped to the pressure position.

An upper guide plate 366 is provided (see also Figure 21) having the recess 36! for the pressure roll :35] and having the guide recess 362 for passageof thepaper aroundfeed roll 35!) prior to the entry'of paper into the interior of drumi59. When the paper emerges from the drum 59 onthe other side, it is appropriately guided by the further recess 363 cooperating with the guide plate 369.

Clamping plate 365 is mounted beneath the guide plate 369 (see Figures 19 and 21). The clamping plate 365 has a lower surface 366 which matches and completes the inner'circular surface of the drum 59. Clamping plate 365 also has a curved surface 361 on its left side which matches the lower portion of roll 356 and which is continuous in the clamped position with surface 362 of guide plate 369. Clamping plate 365 also has a right hand curved surface 363 which is continuous with the guide surface 363 of the guide plate.

Surfaces 310 of guide plate 339 and 3' of clamping plate 365 match each other but, in

operation, with paper being fed through the drum,

are not incontact with each other.

The surfaces 367! and 368 of clamping plate 365 when the clamping plate is in clamping engagement prevent any motion of the paper 25!] with respectto the drum 59, and thus' resist any slight torque which may arise fromthe movement of the pencil with respect to thepaper.

Clamping plate 365 is biased upwardly into clamping engagement with the paper by :means of the spring loaded pins 389, 3311 (Figures 19 and '21). Each of the pins 369 passes through a counterbored opening 38! in the guide plate 360 normal to the surface 316 of the-said guide plate; the lower end of each pin 39!! is threaded at 382 so that it may engage in the tapped openin'g383 'of the clamping plate 365.

Openings 38! in the guide plate 360 are each counterboredat 386 to receive the stop bushing 38"! on each of the pins 389 which limit downward movementof the pins 389 and consequently downward movement of the clamping plate 365.

The upper end of each of the pins 389 is threaded at 389 to receive the nut 390.

A clamp operating cross-shaft 39l is provided rotatably mounted in suitable bearings and carrying the crank arms 392 (see also Figures 20 and 22). Crank arms 392 are keyed to the shaft 39! in any suitable manner and are each provided with openings 393 through which the pins 389 with nuts 39!] pass. The crank arm 392 extends above the bushing 381.

A compression spring 394 is provided around the upper end of each pin 389 between the upper surface of the crank arm 392 and the under-surface of nut 399. Since the crank arm 392 is ordinarily stationary, the compression spring 394 normally biases the pin 389 upwardly by bearing against the nut 399 thereon and accordingly biases the clamp 365 upwardly into clamping engagement. The force exerted by the compression spring 396 may be varied by the adjustment 0 nuts 390.

An appropriate housing 490 may be provided over the pins 386, the clamp operating shaft 39! and the cranks For ordinary operation, after a picture has been recorded, the paper will be fed forward for an additional recording frame; and to make possible this feeding of the paper, the shaft 39l will be rotated clockwise, with respect to Figure 19, to depress the bushing 33! and hence the pins 380, and thus to depress the clamp 365 to release the paper from clamped engagement.

In ordinary operation, the rotation of the clamp operating shaft 39E is automatic to release the paper 256 (and the supply roll 250a and the delivered marked sheet 359') only at the end of a complete picture scanning operation and to cause the picture to be fed forward for one frame only. It may be necessary, however, in appropriate cases, to thread the paper through the machine or to feed the paper forward irrespective of any picture record that may be placed thereon. Accordingly; the shaft 39l provided with an additional manually operated crank cs2 (Figures 19, 20 and 23) which is keyed to the 39! and the end of which extends out slightly from the housing 499. Crank 492 may thus be manually depressed to rotate the shaft 39! and release the clamp 365.

An additional guide element 494 may be provided (Figure 19) on the drum '56 adjacent the of the paper 259 between rolls 35ll-and 351.

The apparatus may also be provided with a picture viewing bed plate All) onto which the scanned paper 250 may be fed. This plate 4|!) may be curved at All to cooperate with curved surface 363 of guideplate 360 and curved surface 368 of the clamping plate 365 to form a passage for the paper out of the drum.

The sides of the bed plate 419 are provided with fianges' ll 9a at the edges overlying the surface of the bed plate and spaced from the surface'by slightly more than the thickness of the paper 259, the inner edges of the flanges being spaced from each other by less than the width of the paper 259. The flanges Alllla accordingly hold the paper firmly on the bed plate 419 even that form of construction in which the bed plate 4H3 is vertical while, nevertheless, permitting the paper to move freely with respect to the plate 410.

The feed roll 359, in addition to being operated by the motor at appropriate'intervals to feed successive lengths'of paper into the drum, may be manually operated by a handle 3 to feed the paper forward.

The machine as a whole may be operated by the handles M4, 414 connected to the principal gears 30, 30 to adjust the apparatus.

In order to thread the paper through the machine, handle 354 is rotated counterclockwise to release the pressure roll 35f from the feed roll 350. The paper 250 is then passed u over the guide 404 around the feed roll-350, being guided by the guide surface 362. The crank 402 is depressed, releasing the clamp 365, and the paper is further pushed past the clamp 365 along the guide surface 366 into the interior of the drum 50. Continuous pushing of the paper or slow operation of the feed roll 350 with the pressure roll 35! engaged therewith will now feed. the paper around the interior of the drum until the edge of the paper emerges on the opposite side. The paper will then move past the curved surface 358 of the clamp and the curved surface 363 of the guide plate 350 and around the curved surface 4 of the viewing plate to emerge upon the viewing plate.

The only feed roll required is the feed roll 350.

The slight back pressure on the paper, owing to friction of the paper against the inside of drum 50 and the surface of viewing plate 4l0, will cause the paper to curve around to hug the interior of the drum 50. In order to increase this back pressure, a spring biased plate (not shown) may be mounted at the left hand end of the bed plate MD (with respect to Figure 19). immediately following the curve 411 to create back pressure on the paper. On release of the crank 402, the clamping plate 365 engages the paper tightly and prevents any movement thereof.

On completion of a scanning operation, the clamp 365 is disengaged and the rotation of feed roll 350 causes the paper to move once more. The scanned sheet may be rolled up on a take-up roll or it may be cut off as each picture is completed.

Where a take-up roll is used, its speed is so adjusted that it does not give the paper any greater linear speed than that imparted to the paper by the feed roll 350, and, in fact, the takeup roll should give the paper a slightly lesser linear speed so that there will be sufficient slack on the paper to create sufficient friction to cause the paper to hu the interior of the drum 50. Thepaper should, of course, be sufiiciently strong and stiff so that it will not crumple when fed around the interior of the drum by the feed roll 350. The paper should, nevertheless, be sufficiently flexible so that it will properly hug the interior surface of drum 50. I have found that an optimum paper for this purpose is a white bond paper .003" to .004 thick.

Instead of a take-up roll, a preferred form is to utilize means for cuttin off the sheet automatically at each picture frame. Thus, as indicated at Figure 19, a completed picture is fed out on the paper 250' on the viewing plate M0. The picture may be examined, and, if necessary, torn off against straight edge 420 of the guide plate 360. However, if the paper is not thus torn off, then at the conclusion of the next scanning operation, the scanned picture 250' is fed forward beneath the cutting knife 42| which cooperates with the edge 422 of the viewing plate 0 and is mounted on the crank 423, which crank is mounted on the shaft 424.

Shaft 424 may be adjusted for rotation in a counterclockwise direction over an angle of about 60 whenever the clamp 365.is released. In other words, shafts 424 and 3% may be connected by a link in any suitable manner for simultaneous operation. Thus, when the clamp 355 is released for feeding the sheet forward, knife 42l,may be depressed beneath the surface of plate 4H). On completion of the feeding operation, when a new picture frame is moved onto the viewing plate 410, the raising of the clamping plate 365 will be accompanied by simultaneous raising of the knife 42!. In this case, the knife may have its cutting edge at its upper end 425 and cooperate with a cross bar 426 having an appropriate cutting edge and arranged above the viewing plate H0 as shown in Figure 19.

Where the upper cross bar 426 is not used, the picture which moves ofi the viewing plate 410 will not be out immediately after being moved off but rather at the completion of the next succeeding scanning cycle; While with the use of the upper cross bar 425, the picture on the viewing plate 410 will be cut off immediately after it is fed forward without waiting for the next succeeding scanning cycle.

The essential elements of the control mechanism for the various devices herein described are shown in the upper portion of Figure l.

Worm 26 on shaft l5 engages with the worm gear 500 on shaft 50L Shaft 51 rotates at the same speed as gears 30 and 30' and thus rotates at the same speed as thepencil inside the drum.

Two cams 502 and 503 are provided to operate the switches 504 and 505 respectively. Switch 504 is connected in series with the coil of the pencil operating apparatus of Figure 6. When switch 504 is open, there is no current to the pencil mechanism. Cam 502 is arranged so that it will open the switch 504 for about /9th of a revolution while the pencil traverses the surface 355 of the clamps 365; thus, the pencil will make no mark on the interior surface of the clamps 365. The purpose of this is to prevent continuous markings on the inner surface of the clamping bar which additively will have the effect of producing a thick coat of graphite which may later be shaken down onto one of the scanned pictures. By this means also, the pencil is not advanced into contact with the surface of the drum or with the paper on the drum at the juncture between the paper and the clamp on either side. This also prevents any possible breakage or scaling of the pencil point.

When the extended surface of cam 502 moves out of engagement with switch 504, then the circuit to the coil N5 of the pencil mechanism is closed so that markings may be made on the paper. The other cam 503 on shaft 50! opens a switch 505 in series with the synchronizing circuit. The opening of this switch 504 thus disconnects the synchronizing circuit at the instant that the pencil passes the center of plate 365 (Figure 19) and maintains contact 505 open for about rotation. The specific operation of switch 505 will be explained in connection with the explanation of the synchronizing elements hereinafter set forth.

Worm 521 also meshes with the worm gear 5l0 which is freely rotatable about the shaft 5|2. The gear 510 may, however, be connected by the clutch 5|4 to rotate the shaft 5!2 and hence to rotate the cam 5|5 mounted on the shaft 512. The operation of clutch 514 is disclosed in Figure 24.

When advance of the paper is desired, a signal 

